The human heart is a four chambered, muscular organ that provides blood circulation through the body during a cardiac cycle. The four main chambers include the right atria and right ventricle which supplies the pulmonary circulation, and the left atria and left ventricle which supplies oxygenated blood received from the lungs to the remaining body. To insure that blood flows in one direction through the heart, atrioventricular valves (tricuspid and mitral valves) are present between the junctions of the atria and the ventricles, and semi-lunar valves (pulmonary valve and aortic valve) govern the exits of the ventricles leading to the lungs and the rest of the body. These valves contain leaflets or cusps that open and shut in response to blood pressure changes caused by the contraction and relaxation of the heart chambers. The leaflets move apart from each other to open and allow blood to flow downstream of the valve, and coapt to close and prevent backflow or regurgitation in an upstream manner.
Diseases associated with heart valves, such as those caused by damage or a defect, can include stenosis and valvular insufficiency or regurgitation. For example, valvular stenosis causes the valve to become narrowed and hardened which can prevent blood flow to a downstream heart chamber or structure (e.g., aorta) to occur at the proper flow rate and cause the heart to work harder to pump the blood through the diseased valve. Aortic stenosis, for example, can lead to chest pain, fainting, and heart failure. Valvular insufficiency or regurgitation occurs when the valve does not close completely, allowing blood to flow backwards, thereby causing the heart to be less efficient. For example, aortic valvular insufficiency results in blood pooling in the left ventricle which must then expand its normal capacity to accommodate the pooled volume of blood as well as the new blood received in the subsequent cardiac cycle. For this reason the heart muscle must work harder to pump the extra volume of blood which causes strain of the heart muscle over time as well as raises the blood pressure in the heart. A diseased or damaged valve, which can be congenital, age-related, drug-induced, or in some instances, caused by infection, can result in an enlarged, thickened heart that loses elasticity and efficiency. Other symptoms of heart valve diseases, such as stenosis and valvular insufficiency, can include weakness, shortness of breath, dizziness, fainting, palpitations, anemia and edema, and blood clots which can increase the likelihood of stroke or pulmonary embolism. Such symptoms can often be severe enough to be debilitating and/or life threatening.
Prosthetic heart valves have been developed for repair and replacement of diseased and/or damaged heart valves. Such valves can be percutaneously delivered and deployed at the site of the diseased heart valve through catheter-based systems. Such prosthetic heart valves can be delivered while in a low-profile or compressed/contracted arrangement so that the prosthetic valves can be contained within a sheath component of a delivery catheter and advanced through the patient's vasculature. Once positioned at the treatment site, the prosthetic valves can be expanded to engage tissue at the diseased heart valve region to, for instance, hold the prosthetic valve in position. While these prosthetic valves offer minimally invasive methods for heart valve repair and/or replacement, challenges remain to provide prosthetic valves that prevent leakage between the implanted prosthetic valve and the surrounding tissue (paravalvular leakage) and for preventing movement and/or migration of the prosthetic valve that could occur during the cardiac cycle. For example, the repair or replacement of the aortic valve can present numerous challenges due to differing anatomies and etiologies presented by individual patients. The varying shapes, sizes and other features associated with an abnormal or unhealthy aortic valve can prevent proper alignment of the replacement (e.g., prosthetic) valve which can cause leakage, valve impingement or dislodgement of the prosthesis. In a particular example, stenosis of the aortic valve can deform the valvular area which can result in paravalvular leakage around an implanted replacement valve. Additional challenges can include providing a prosthetic valve that can be adjusted or repositioned during or after implantation and/or for replacing a previously implanted prosthetic valve.